5-Carboxycytosine-13C,15N2 is doubly labeled 5-Carboxycytosine (C177975). Cytosine derivatives, such as 5-Carboxylcytosine, are involved with a wide variety of biological functions including cytosine methylation, gene expression, genome stability, and chromatin modification. In addition, 5-Carboxylcytosine interacts with the RNA polymerase II elongation complex that can influence the pluripotent states during early embryonic development.